Free/Busy Information not available to Outlook 2007 users Exch2007 in coexistense with Exch2003

I'm running Exchange 2007 SP1 in coexistence with Exchange 2003 & am in the process of migrating mailboxes. The majority of our users are on Outlook 2003 but some (including myself) are running Outlook 2007. Outlook 2007 users are unable to view free/busy information when scheduling appointments but Outlook 2003 users are. I f I try to view a colleagues free/busy information using Outlook 2007 I fail where if I use Outlook 2003 it works. My maiolbox is on Exchange 2007. I have replicated Public Folders from Exchange 2003 to 2007.

Thanks for the responses, much appreciated! I've managed to fix the issue by simply creating a DNS A record for the Autodiscover server on our domain, slightly embarrassing!
We know have the situation that Outlook 2007 clients whos mailbox is on Exchange 2007 cant see free/busy information for users who are using Outlook 2003 regardless of whether their mailbox is on Exchange 2003 or 2007! Any more ideas?

It seems 2007 free/busy doesn't have 2003 replica. Also check the replication schedule for both FB folders. Set it to always. If it doesn't resolve your issue then enable diagnostic logging and see if there any errors in replication.

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